Weld neck flange is a type of pipe flange that incorporates a cast-in neck that is welded to the pipe. Unlike a plain flange that is slipped over the pipe prior to being welded into place, a weld neck flange has a spout-like neck that is beveled to match up to the pipe. Once the pipe is beveled to match the weld neck flange, a perfect V shape is created in which a butt weld is placed to connect the two components.